import java.awt.*;
import java.util.*;
import java.applet.Applet;

public class Converter extends Applet {
    Frame window;
    ConversionPanel metricPanel, usaPanel;
    Unit metricDistances[] = new Unit[3];
    Unit usaDistances[] = new Unit[4];

    /** Create the ConversionPanels (one for metric, another for U.S.).
      * I used "U.S." because although Imperial and U.S. distance
      * measurements are the same, this program could be extended to
      * include volume measurements, which aren't the same.
      */
    public void init() {
        setLayout(new GridLayout(2,0,5,5));

        metricDistances[0] = new Unit("Centimeters", 0.01);
        metricDistances[1] = new Unit("Meters", 1.0);
        metricDistances[2] = new Unit("Kilometers", 1000.0);
        metricPanel = new ConversionPanel(this, "Metric System",
                                          metricDistances);

        usaDistances[0] = new Unit("Inches", 0.0254);
        usaDistances[1] = new Unit("Feet", 0.305);
        usaDistances[2] = new Unit("Yards", 0.914);
        usaDistances[3] = new Unit("Miles", 1613.0);
        usaPanel = new ConversionPanel(this, "U.S. System", usaDistances);

        add(metricPanel);
        add(usaPanel);
    }

    /** Does the conversion from metric to U.S., or vice versa, and
      * updates the appropriate ConversionPanel. */
    void convert(ConversionPanel from) {
        ConversionPanel to;

        if (from == metricPanel)
            to = usaPanel;
        else
            to = metricPanel;
        double multiplier = from.getMultiplier() / to.getMultiplier();
        to.setValue(from.getValue() * multiplier);
    }

    /** Draws a box around this panel. */
    public void paint(Graphics g) {
        Dimension d = size();
        g.drawRect(0,0, d.width - 1, d.height - 1);
    }

    /** Puts a little breathing space between
      * the panel and its contents, which lets us draw a box
      * in the paint() method.
      */
    public Insets insets() {
        return new Insets(5,5,5,5);
    }

    public static void main(String args[]) {
        Frame f = new Frame("Converter Applet/Application");
        Converter converter = new Converter();

        converter.init();

        f.add("Center", converter);
        f.pack();
        f.show();
    }
}

class ConversionPanel extends Panel {
    String title;
    TextField textField;
    Scrollbar slider;
    Choice unitChooser;
    int min = 0;
    int max = 10000;
    Converter controller;
    Unit units[];

    //TO DO: Should make both panels' choices the same width.
    ConversionPanel(Converter myController, String myTitle, Unit myUnits[]) {
        super();
        GridBagConstraints c = new GridBagConstraints();
        GridBagLayout gridbag = new GridBagLayout();
        setLayout(gridbag);
        controller = myController;
        title = myTitle;
        units = myUnits;

        //Set up default constraints
        c.fill = GridBagConstraints.HORIZONTAL;

        //Add the label
        Label label = new Label(title, Label.CENTER);
        c.weightx = 0.0;
        c.gridwidth = GridBagConstraints.REMAINDER;
        gridbag.setConstraints(label, c);
        add(label);

        //Add the text field
        textField = new TextField("0", 10);
        c.weightx = 1.0;
        c.gridwidth = GridBagConstraints.RELATIVE;
        gridbag.setConstraints(textField, c);
        add(textField);

        //Add the pop-up list (Choice)
        unitChooser = new Choice();
        for (int i = 0; i < units.length; i++) {
            unitChooser.addItem(units[i].description);
        }
        c.weightx = 0.0;
        c.gridwidth = GridBagConstraints.REMAINDER;
        gridbag.setConstraints(unitChooser, c);
        add(unitChooser);

        //Add the slider
        slider = new Scrollbar(Scrollbar.HORIZONTAL, 0, 100, min, max);
        c.weightx = 0.0;
        c.gridheight = 1;
        c.gridwidth = GridBagConstraints.RELATIVE;
        gridbag.setConstraints(slider, c);
        add(slider);
    }

    /** Returns the multiplier (units/meter) for the currently
      * selected unit of measurement.
      */
    double getMultiplier() {
        int i = unitChooser.getSelectedIndex();
        return (units[i].multiplier);
    }

    /** Draws a box around this panel. */
    public void paint(Graphics g) {
        Dimension d = size();
        g.drawRect(0,0, d.width - 1, d.height - 1);
    }

    /** Puts a little breathing space between
      * the panel and its contents, which lets us draw a box
      * in the paint() method.
      * We add more pixels to the right, to work around a
      * Choice bug.
      */
    public Insets insets() {
        return new Insets(5,5,5,8);
    }

    /** Gets the current value in the text field.
      * That's guaranteed to be the same as the value
      * in the scroller (subject to rounding, of course).
      */
    double getValue() {
        double f;
        try {
            f = Double.valueOf(textField.getText()).doubleValue();
        } catch (java.lang.NumberFormatException e) {
            f = 0.0;
        }
        return f;
    }

    /** Respond to user actions. */
    public boolean handleEvent(Event e) {
        if (e.target instanceof Scrollbar) {
            textField.setText(String.valueOf(slider.getValue()));
            controller.convert(this);
            return true;
        } else if (e.target instanceof TextField) {
            setSliderValue(getValue());
            controller.convert(this);
            return true;
        } else if (e.target instanceof Choice) {
            controller.convert(this);
            return true;
        }
        return false;
    }

    /** Set the values in the slider and text field. */
    void setValue(double f) {
        setSliderValue(f);
        textField.setText(String.valueOf(f));
    }

    /** Set the slider value. */
    void setSliderValue(double f) {
        int sliderValue = (int)f;

        if (sliderValue > max)
            sliderValue = max;
        if (sliderValue < min)
            sliderValue = min;
        slider.setValue(sliderValue);
    }
}


class Unit {
    String description;
    double multiplier;

    Unit(String description, double multiplier) {
        super();
        this.description = description;
        this.multiplier = multiplier;
    }

    public String toString() {
        String s = "Meters/" + description + " = " + multiplier;
        return s;
    }
}